A NAND flash memory is widespread as a storage device for large volume data. Currently, a reduction in cost and an increase in capacity per bit are promoted by refining a storage device.
On the other hand, it is also expected that a new storage device (hereinafter simply referred to as memory) based on an operation principle different from that of the floating flash memory in the past will be put to practical use.
For example, a two-terminal memory represented by a resistive random access memory (ReRAM) is prospective as a next-generation memory from the viewpoint of, for example, easiness in a low-voltage operation, high-speed switching, and refining. Examples of the two-terminal memory include a memory in which an amorphous silicon layer (hereinafter also referred to as a-Si layer in abbreviation) is used as a variable resistance layer. In such a two-terminal memory, to facilitate application to a large-capacity memory or the like, it is demanded that the low-voltage operation is possible even when the variable resistance layer is formed on a semiconductor substrate.